unit bufdataset_parser;

{$h+}
{$mode delphi}


interface

uses
  SysUtils,
  Classes,
  db,
  dbf_prscore,
  dbf_prsdef;

type

  TBufDatasetParser = class(TCustomExpressionParser)
  private
    FDataset: TDataSet;
    FFieldVarList: TStringList;
    FResultLen: Integer;
    FIsExpression: Boolean;       // expression or simple field?
    FFieldType: TExpressionType;
    FCaseInsensitive: Boolean;
    FPartialMatch: boolean;

  protected
    FCurrentExpression: string;

    procedure FillExpressList; override;
    procedure HandleUnknownVariable(VarName: string); override;
    function  GetVariableInfo(VarName: string): TField;
    function  CurrentExpression: string; override;
    function  GetResultType: TExpressionType; override;

    procedure SetCaseInsensitive(NewInsensitive: Boolean);
    procedure SetPartialMatch(NewPartialMatch: boolean);
  public
    constructor Create(ADataset: TDataset);
    destructor Destroy; override;

    procedure ClearExpressions; override;

    procedure ParseExpression(AExpression: string); virtual;
    function ExtractFromBuffer(Buffer: PChar): PChar; virtual;

    property Dataset: TDataSet read FDataset; // write FDataset;
    property Expression: string read FCurrentExpression;
    property ResultLen: Integer read FResultLen;

    property CaseInsensitive: Boolean read FCaseInsensitive write SetCaseInsensitive;
    property PartialMatch: boolean read FPartialMatch write SetPartialMatch;
  end;

implementation

uses dbconst;

type
// TFieldVar aids in retrieving field values from records
// in their proper type

  TFieldVar = class(TObject)
  private
    FField: TField;
    FFieldName: string;
    FExprWord: TExprWord;
  protected
    function GetFieldVal: Pointer; virtual; abstract;
    function GetFieldType: TExpressionType; virtual; abstract;
  public
    constructor Create(UseField: TField);

    procedure Refresh(Buffer: PChar); virtual; abstract;

    property FieldVal: Pointer read GetFieldVal;
    property FieldDef: TField read FField;
    property FieldType: TExpressionType read GetFieldType;
    property FieldName: string read FFieldName;
  end;

  TStringFieldVar = class(TFieldVar)
  protected
    FFieldVal: PChar;

    function GetFieldVal: Pointer; override;
    function GetFieldType: TExpressionType; override;
  public
    constructor Create(UseField: TField);
    destructor Destroy; override;

    procedure Refresh(Buffer: PChar); override;
  end;

  TFloatFieldVar = class(TFieldVar)
  private
    FFieldVal: Double;
  protected
    function GetFieldVal: Pointer; override;
    function GetFieldType: TExpressionType; override;
  public
    procedure Refresh(Buffer: PChar); override;
  end;

  TIntegerFieldVar = class(TFieldVar)
  private
    FFieldVal: Integer;
  protected
    function GetFieldVal: Pointer; override;
    function GetFieldType: TExpressionType; override;
  public
    procedure Refresh(Buffer: PChar); override;
  end;

  TLargeIntFieldVar = class(TFieldVar)
  private
    FFieldVal: Int64;
  protected
    function GetFieldVal: Pointer; override;
    function GetFieldType: TExpressionType; override;
  public
    procedure Refresh(Buffer: PChar); override;
  end;

  TDateTimeFieldVar = class(TFieldVar)
  private
    FFieldVal: TDateTime;
    function GetFieldType: TExpressionType; override;
  protected
    function GetFieldVal: Pointer; override;
  public
    procedure Refresh(Buffer: PChar); override;
  end;

  TBooleanFieldVar = class(TFieldVar)
  private
    FFieldVal: wordbool;
    function GetFieldType: TExpressionType; override;
  protected
    function GetFieldVal: Pointer; override;
  public
    procedure Refresh(Buffer: PChar); override;
  end;

//--TFieldVar----------------------------------------------------------------
constructor TFieldVar.Create(UseField: TField);
begin
  inherited Create;

  // store field
  //FDataset := ADataset;
  FField := UseField;
  FFieldName := UseField.FieldName;
end;

//--TStringFieldVar-------------------------------------------------------------
function TStringFieldVar.GetFieldVal: Pointer;
begin
  Result := @FFieldVal;
end;

function TStringFieldVar.GetFieldType: TExpressionType;
begin
  Result := etString;
end;

constructor TStringFieldVar.Create(UseField: TField);
begin
  inherited;

  GetMem(FFieldVal, dsMaxStringSize+1);
end;

destructor TStringFieldVar.Destroy;
begin
  FreeMem(FFieldVal);

  inherited;
end;

procedure TStringFieldVar.Refresh(Buffer: PChar);
var Fieldbuf : TStringFieldBuffer;
    s        : string;
begin
  if not FField.DataSet.GetFieldData(FField,@Fieldbuf) then
    s := ''
  else
    s := Fieldbuf;
  strcopy(FFieldVal,@s[1]);
end;

//--TFloatFieldVar-----------------------------------------------------------
function TFloatFieldVar.GetFieldVal: Pointer;
begin
  Result := @FFieldVal;
end;

function TFloatFieldVar.GetFieldType: TExpressionType;
begin
  Result := etFloat;
end;

procedure TFloatFieldVar.Refresh(Buffer: PChar);
begin
  if not FField.DataSet.GetFieldData(FField,@FFieldVal) then
    FFieldVal := 0;
end;

//--TIntegerFieldVar----------------------------------------------------------
function TIntegerFieldVar.GetFieldVal: Pointer;
begin
  Result := @FFieldVal;
end;

function TIntegerFieldVar.GetFieldType: TExpressionType;
begin
  Result := etInteger;
end;

procedure TIntegerFieldVar.Refresh(Buffer: PChar);
begin
  if not FField.DataSet.GetFieldData(FField,@FFieldVal) then
    FFieldVal := 0;
end;

//--TLargeIntFieldVar----------------------------------------------------------
function TLargeIntFieldVar.GetFieldVal: Pointer;
begin
  Result := @FFieldVal;
end;

function TLargeIntFieldVar.GetFieldType: TExpressionType;
begin
  Result := etLargeInt;
end;

procedure TLargeIntFieldVar.Refresh(Buffer: PChar);
begin
  if not FField.DataSet.GetFieldData(FField,@FFieldVal) then
    FFieldVal := 0;
end;

//--TDateTimeFieldVar---------------------------------------------------------
function TDateTimeFieldVar.GetFieldVal: Pointer;
begin
  Result := @FFieldVal;
end;

function TDateTimeFieldVar.GetFieldType: TExpressionType;
begin
  Result := etDateTime;
end;

procedure TDateTimeFieldVar.Refresh(Buffer: PChar);
begin
  if not FField.DataSet.GetFieldData(FField,@FFieldVal) then
    FFieldVal := 0;
end;

//--TBooleanFieldVar---------------------------------------------------------
function TBooleanFieldVar.GetFieldVal: Pointer;
begin
  Result := @FFieldVal;
end;

function TBooleanFieldVar.GetFieldType: TExpressionType;
begin
  Result := etBoolean;
end;

procedure TBooleanFieldVar.Refresh(Buffer: PChar);
begin
  if not FField.DataSet.GetFieldData(FField,@FFieldVal) then
    FFieldVal := False;
end;

//--TBufDatasetParser---------------------------------------------------------------

constructor TBufDatasetParser.Create(Adataset: TDataSet);
begin
  FDataset := Adataset;
  FFieldVarList := TStringList.Create;
  FCaseInsensitive := true;
  inherited Create;
end;

destructor TBufDatasetParser.Destroy;
begin
  ClearExpressions;
  inherited;
  FreeAndNil(FFieldVarList);
end;

function TBufDatasetParser.GetResultType: TExpressionType;
begin
  // if not a real expression, return type ourself
  if FIsExpression then
    Result := inherited GetResultType
  else
    Result := FFieldType;
end;

procedure TBufDatasetParser.SetCaseInsensitive(NewInsensitive: Boolean);
begin
  if FCaseInsensitive <> NewInsensitive then
  begin
    // clear and regenerate functions
    FCaseInsensitive := NewInsensitive;
    FillExpressList;
  end;
end;

procedure TBufDatasetParser.SetPartialMatch(NewPartialMatch: boolean);
begin
  if FPartialMatch <> NewPartialMatch then
  begin
    // refill function list
    FPartialMatch := NewPartialMatch;
    FillExpressList;
  end;
end;

procedure TBufDatasetParser.FillExpressList;
var
  lExpression: string;
begin
  lExpression := FCurrentExpression;
  ClearExpressions;
  FWordsList.FreeAll;
  FWordsList.AddList(DbfWordsGeneralList, 0, DbfWordsGeneralList.Count - 1);
  if FCaseInsensitive then
  begin
    FWordsList.AddList(DbfWordsInsensGeneralList, 0, DbfWordsInsensGeneralList.Count - 1);
    if FPartialMatch then
    begin
      FWordsList.AddList(DbfWordsInsensPartialList, 0, DbfWordsInsensPartialList.Count - 1);
    end else begin
      FWordsList.AddList(DbfWordsInsensNoPartialList, 0, DbfWordsInsensNoPartialList.Count - 1);
    end;
  end else begin
    FWordsList.AddList(DbfWordsSensGeneralList, 0, DbfWordsSensGeneralList.Count - 1);
    if FPartialMatch then
    begin
      FWordsList.AddList(DbfWordsSensPartialList, 0, DbfWordsSensPartialList.Count - 1);
    end else begin
      FWordsList.AddList(DbfWordsSensNoPartialList, 0, DbfWordsSensNoPartialList.Count - 1);
    end;
  end;
  if Length(lExpression) > 0 then
    ParseExpression(lExpression);
end;

function TBufDatasetParser.GetVariableInfo(VarName: string): TField;
begin
  Result := FDataset.FindField(VarName);
end;

function TBufDatasetParser.CurrentExpression: string;
begin
  Result := FCurrentExpression;
end;

procedure TBufDatasetParser.HandleUnknownVariable(VarName: string);
var
  FieldInfo: TField;
  TempFieldVar: TFieldVar;
begin
  // is this variable a fieldname?
  FieldInfo := GetVariableInfo(VarName);
  if FieldInfo = nil then
    raise EDatabaseError.CreateFmt(SErrIndexBasedOnUnkField, [VarName]);

  // define field in parser
  case FieldInfo.DataType of
    ftString, ftFixedChar:
      begin
      TempFieldVar := TStringFieldVar.Create(FieldInfo);
      TempFieldVar.FExprWord := DefineStringVariable(VarName, TempFieldVar.FieldVal);
      TempFieldVar.FExprWord.fixedlen := Fieldinfo.Size;
      end;
    ftBoolean:
      begin
        TempFieldVar := TBooleanFieldVar.Create(FieldInfo);
        TempFieldVar.FExprWord := DefineBooleanVariable(VarName, TempFieldVar.FieldVal);
      end;
    ftFloat:
      begin
        TempFieldVar := TFloatFieldVar.Create(FieldInfo);
        TempFieldVar.FExprWord := DefineFloatVariable(VarName, TempFieldVar.FieldVal);
      end;
    ftAutoInc, ftInteger, ftSmallInt:
      begin
        TempFieldVar := TIntegerFieldVar.Create(FieldInfo);
        TempFieldVar.FExprWord := DefineIntegerVariable(VarName, TempFieldVar.FieldVal);
      end;
    ftLargeInt:
      begin
        TempFieldVar := TLargeIntFieldVar.Create(FieldInfo);
        TempFieldVar.FExprWord := DefineLargeIntVariable(VarName, TempFieldVar.FieldVal);
      end;
    ftDate, ftDateTime:
      begin
        TempFieldVar := TDateTimeFieldVar.Create(FieldInfo);
        TempFieldVar.FExprWord := DefineDateTimeVariable(VarName, TempFieldVar.FieldVal);
      end;
  else
    raise EDatabaseError.CreateFmt(SErrIndexBasedOnInvField, [VarName,Fieldtypenames[FieldInfo.DataType]]);
  end;

  // add to our own list
  FFieldVarList.AddObject(VarName, TempFieldVar);
end;

procedure TBufDatasetParser.ClearExpressions;
var
  I: Integer;
begin
  inherited;

  // test if already freed
  if FFieldVarList <> nil then
  begin
    // free field list
    for I := 0 to FFieldVarList.Count - 1 do
    begin
      // replacing with nil = undefining variable
      FWordsList.DoFree(TFieldVar(FFieldVarList.Objects[I]).FExprWord);
      TFieldVar(FFieldVarList.Objects[I]).Free;
    end;
    FFieldVarList.Clear;
  end;

  // clear expression
  FCurrentExpression := EmptyStr;
end;

procedure TBufDatasetParser.ParseExpression(AExpression: string);
var
  TempBuffer: pchar;
begin
  // clear any current expression
  ClearExpressions;

  // is this a simple field or complex expression?
  FIsExpression := GetVariableInfo(AExpression) = nil;
  if FIsExpression then
  begin
    // parse requested
    CompileExpression(AExpression);

    // determine length of string length expressions
    if ResultType = etString then
    begin
      // make empty record
      GetMem(TempBuffer, FDataset.RecordSize);
      try
        FillChar(TempBuffer^, FDataset.RecordSize, #0);
        FResultLen := StrLen(ExtractFromBuffer(TempBuffer));
      finally
        FreeMem(TempBuffer);
      end;
    end;
  end else begin
    // simple field, create field variable for it
    HandleUnknownVariable(AExpression);
    FFieldType := TFieldVar(FFieldVarList.Objects[0]).FieldType;
    // set result len of variable length fields
    if FFieldType = etString then
      FResultLen := TFieldVar(FFieldVarList.Objects[0]).FieldDef.Size
  end;

  // set result len for fixed length expressions / fields
  case ResultType of
    etBoolean:  FResultLen := 1;
    etInteger:  FResultLen := 4;
    etFloat:    FResultLen := 8;
    etDateTime: FResultLen := 8;
  end;

  // check if expression not too long
  if FResultLen > 100 then
    raise EDatabaseError.CreateFmt(SErrIndexResultTooLong, [AExpression, FResultLen]);

  // if no errors, assign current expression
  FCurrentExpression := AExpression;
end;

function TBufDatasetParser.ExtractFromBuffer(Buffer: PChar): PChar;
var
  I: Integer;
begin
  // prepare all field variables
  for I := 0 to FFieldVarList.Count - 1 do
    TFieldVar(FFieldVarList.Objects[I]).Refresh(Buffer);

  // complex expression?
  if FIsExpression then
  begin
    // execute expression
    EvaluateCurrent;
    Result := ExpResult;
  end else begin
    // simple field, get field result
    Result := TFieldVar(FFieldVarList.Objects[0]).FieldVal;
    // if string then dereference
    if FFieldType = etString then
      Result := PPChar(Result)^;
  end;
end;

end.

